(spazm) [Gr. spasmos, convulsion] A sudden, involuntary movement or muscular contraction due to an irritant or trauma. Spasms may be clonic or tonic and involve either visceral muscle or skeletal muscle. When contractions are strong and painful, they are called cramps. The effect of the spasm depends on the part affected: asthma is at least partly the result of bronchospasm; renal colic to spasm of the muscular coat of the ureter.